They were concerned that perverts would try to catch peeks of the girls in actions.

The TNW Tulip sports hall is home to four individual gymnastics clubs and is used exclusively for practice and competitions. Located in the center of Utrecht, the hall is part of a much larger redeveloped sports complex and is situated next to a school and a soccer club. The hall includes a large open space for practice and competitions, along with offices, locker rooms, bathrooms, and a top floor viewing area for spectators.

The developers of the club decided it would be best if there were no windows at all in the building on the sides. This was for three reasons. First, for serious training and competition, windows can cause undesirable effects like glare, too much contrast or distractions. Second, the area is not the safest and the streets surrounding it used to be covered in shattered glass from cars being broken into, so minimizing glass on the building was also for safety. And thirdly, since many young girls would be practicing inside, the developers thought it best to eliminate the ability for anyone to look inside.

But without any windows at all, gymnastics halls tend to be dark, gloomy and lit with fluorescent lights. Wanting a better solution they tasked NL Architects to come up with a better alternative. Their solution was to peel away the sides of the walls at the top to let natural daylight in. Since the facade bends at the top, light infiltrates in and reflects off the sides of the walls. Additional skylights in the roof along with artificial lights provide more light for the space below. The result is a bright and pleasant space that meets all of the requirements of the gymnastics hall.